1. Field of the Invention
The present invention is directed generally to methods and apparatus for positioning an intraluminal graft. More specifically the present invention is related to methods and apparatus for positioning an intraluminal graft into a bifurcating vessel such as an artery.
2. Discussion of Related Technology
An artery or other vessel that is weakened by disease, injury, or congenital defect, can become distended due to the pressure of blood or other fluid flowing through the weakened area. In the vasculature, this distended weakening is called an aneurysm. An aneurysm typically occurs in the arterial vessels of the head, chest, or abdomen. The distension may cause the vessel to rupture, which can have serious, even life-threatening consequences.
Aneurysms in the abdominal aorta are typically distended around the circumference of the aorta and tapered at both ends. Most aneurysms of the abdominal aorta are caused by atherosclerotic weakening of a segment of the wall. Abdominal aneurysms may cause backache and severe pain, and may be visible as a throbbing swelling. If an abdominal aorta ruptures, it is seriously life threatening.
Traditionally, aneurysms have been treated by radical surgical graft replacement. This approach is risky for the patient and is sometimes not feasible due to other pre-existing disease states of the patient. More recently, aneurysms have been treated by placement of an intraluminal or endovascular graft. These intraluminal or endovascular grafts may be of various types, including grafts having stents, wireforms, or other attachment means attached to or integrated into the graft structure.
In general, intraluminal grafts and their respective support and/or attachment means fall into two major categories, self-expanding and pressure expandable. Self-expanding intraluminal grafts, are supported and/or attached via resilient or shape-memory material such as spring steel or Nitinol(trademark). Self-expanding material is capable of being formed in a configuration from which it may be compressed to a radially compact diameter for placement within a damaged vessel. At the time of use, the memory feature of these materials causes them to self-expand from the radially compact diameter to the expanded operative diameter.
Pressure-expandable intraluminal grafts are supported and/or attached via plastically deformable material such as stainless steel that is initially formed in its radially compact diameter. This type of material does not have memory, and will remain in the radially compact diameter until manually expanded. Typically, outwardly directed pressure is exerted upon the graft through use of a balloon so as to cause radial expansion and resultant plastic deformation of the material to its operative diameter.
Careful positioning and firm implantation of the intraluminal graft is critical to the successful treatment of the underlying medical condition. This is particularly difficult to accomplish when the aneurysm extends from an artery into one or more divergent arteries. A xe2x80x9ctrouser graftxe2x80x9d has been suggested for use in a first main artery and a pair of divergent arteries by White et al. in PCT Application Nos. WO 97/17910; WO 97/17911; WO 97/18006; WO 97/26936; and WO 97/26938; all of which are hereby incorporated herein by reference in their entireties. A trouser graft comprises a first tubular body that bifurcates into two smaller tubular bodies. In the referenced disclosures, the first tubular body is placed in first artery and the two smaller tubular bodies are placed so as to extend within the two divergent arteries.
Notwithstanding the important teachings of the foregoing references, features of the aforementioned device have recognized shortcomings that make them less than complete solutions to the treatment of aneurysms in the vasculature, or to the treatment of similar damage to other vessels. The present invention provides substantial improvements to the methods and apparatus of the prior art.
It is an object of the present invention to provide an improved intraluminal graft and method for placement of same that diminishes deleterious kinking and twisting of the graft during and after placement thereof in a vessel.
It is another object of the present invention to provide an improved intraluminal graft and method for placement of same that provides control over inadvertent longitudinal movement within a vessel.
Another object of the present invention is to provide an improved intraluminal xe2x80x9ctrouserxe2x80x9d graft and method for placement of same that precludes inadvertent separation of the legs of the trouser.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.
To achieve the forgoing objects, and in accordance with the invention as embodied and broadly described herein, the present invention relates to new and useful apparatus and methods for placing a bifurcated graft at the site of a damaged vessel. In a preferred embodiment, the methods and apparatus of the present invention are directed to placement of a bifurcated graft within an aneurysm located in the abdominal aorta downstream of the renal arteries. Preferably, placement of the graft is through the right femoral artery of a patient.
An introducer assembly is provided which is configured for placement over a guidewire and for facilitating the advancement of various catheter assemblies required in connection with the practice of the invention. The introducer assembly includes a sheath, valve head, and a dilator. The sheath is preferably cylindrical in shape and is formed so as to have an appropriate flexibility and an outer diameter suitable for placement at the location of an aneurysm to be repaired. The valve head permits insertion and removal of various catheters during the method of the present invention without significant loss of blood from the femoral artery. The proximal end of the valve head is provided with a threaded connector which facilitates connection of the valve head to other catheters. The dilator, which includes a tapered tip, is placed during use through the valve head and the sheath so that the tapered tip portion protrudes from the sheath. The dilator tip portion is capable of being advanced gently through the tortuous pathway of the vasculature without causing undue trauma or a perforation, yet is also sufficiently stiff to cause the blood vessels to assume a less tortuous path.
Another component of the present invention is a bifurcated aortic graft. The preferred bifurcated aortic graft includes both self-expanding and balloon-expandable wireforms along its length. The balloon-expandable wires permit precision in placement of the aortic graft. The self-expanding wires open within the vessel immediately upon deployment from the main catheter assembly, which allows insertion of other modular components, opens a removal path for the inflatable balloons, and reduces kinking. The self-expanding wires also increase the anchoring force between the bifurcated graft and modular extension grafts used to extend the bifurcated graft into communication with non-distended vessel walls.
One of the self-expanding wireforms is located at a septum region of the bifurcated graft. The septum region separates an ipsilateral leg from a contralateral leg (xe2x80x9cipsilateralxe2x80x9d and xe2x80x9ccontralateralxe2x80x9d referring to opposite lateral sides of the patient depending on the surgical approach). This septum wire prevents and helps eliminate the kinks that are typically encountered with conventional bifurcated grafts. In addition, the self-expanding wireform at the septum region includes crimps functioning as radiopaque markers generally pointing to the septum region, which aids in identifying the location of the septum under fluoroscopy. Two additional self-expanding wireforms are located at the ends of each leg of the bifurcated graft. These wireforms facilitate opening the legs immediately upon deployment from the main catheter assembly to allow for the insertion of modular components. These leg wireforms also contain crimps as radiopaque markers which aid in identifying the ends of the bifurcated graft legs. All crimps on the self-expanding wireforms are placed on the anterior side of the graft, thus aiding in orientation of the graft under fluoroscopy.
The main catheter assembly is utilized to place the aortic graft described above, which is compressed and loaded onto the distal end of the main catheter assembly. The main catheter assembly is sized such that it will fit inside the introducer sheath.
The components of the main catheter assembly include the following: a rigid loader configured for connection to the valve head of the sheath assembly; a proximal connector assembly including a distal pusher connector; an elongate, tubular pusher body; an elongate catheter with a coaxial tube construction; and an inflatable catheter balloon.
In addition to the aortic graft, two additional graft portions are adapted to extend into the respective iliac arteries to form a frictional engagement with the ipsilateral and contralateral legs of the aortic graft. These extension grafts typically comprise straight cylindrical tubes, with an upstream end having a common diameter. The upstream ends interlock with the respective downstream portions of the aortic graft.
The present invention may further include a directional catheter which permits placement of the graft extensions. The directional catheter includes a deflecting spring portion, a knob used to deflect the spring portion, and a connector nut for connection with the sheath assembly.
The preferred method for using the aforementioned components of the present invention includes the following steps. An incision is made and a primary guidewire is placed in conventional fashion in the ipsilateral side, that is, for example, through the right femoral artery and the right common iliac artery so as to extend well upstream of the aneurysm. The introducer assembly is advanced over and along the primary guidewire into a position upstream of the renal arteries. Once the sheath of the introducer assembly has been properly placed, the dilator is retracted along the guidewire and then completely removed from within the sheath assembly and from primary guidewire. The main catheter assembly is inserted over the primary guidewire and into the sheath assembly, and then connected thereto. The pusher body is distally advanced to push the aortic graft and main catheter through to the end of the introducer sheath. The sheath containing the aortic graft is then retracted slowly to approximately a desired deployment position in the abdominal aorta. The introducer sheath is then retracted to a position just below the septum region, freeing the aortic graft and exposing it to blood flow.
The balloon-expandable, upstream portion of the aortic graft remains in a substantially compressed configuration. The catheter balloon is inflated which facilitates the concurrent radial expansion of the balloon-expandable portions of the graft from the initial, collapsed orientation, to the second, expanded orientation. In one embodiment of the present invention, the graft is slightly over-sized to optimize engagement of the aortic graft with the aortic wall. When the graft is fully expanded, the upstream end thereof frictionally engages the luminal surfaces of unaffected regions of the aorta just below the renal arteries. After the graft has been radially expanded in the aforementioned manner, the balloon is deflated, longitudinally stretched to prevent snagging on the graft, and then removed. The main catheter is then withdrawn slowly and carefully, with the introducer sheath and the primary guidewire remaining in place.
For placement of the graft extensions, the directional catheter is first inserted over the primary guidewire through the ipsilateral side, that is, for example, through the right femoral artery and the right common iliac artery. The spring portion of the directional catheter is positioned such that it is above the septal region of the aortic graft. The spring portion is deflected by pulling proximally on the knob. A supplemental guidewire is then advanced through the directional catheter and out the deflected spring portion such that the supplemental guidewire extends down the contralateral leg and through the left common iliac artery. The supplemental guidewire is extended until it is in the left femoral artery, at which time the left femoral artery is cross-clamped and a cut-down or percutaneous incision is performed to retrieve the supplemental guidewire. Once the guidewire is retrieved, a stiffer guidewire is exchanged through the left femoral artery until it is within the first graft and reaches the contralateral side of the aortic graft. A second introducer assembly is then introduced over the stiff guidewire.
A second catheter assembly on which is packaged a tubular graft extension is then introduced through the second sheath assembly until the introducer sheath extends through the left iliac artery and terminates at the bifurcation point of the aortic graft. The sheath followed by the pusher of the second catheter assembly are then pulled back proximally to release the tubular graft extension. The balloon on the second catheter assembly is then inflated such that the upstream end of the extension graft is frictionally engaged with the downstream contralateral leg of the aortic graft. In one embodiment of the present invention, the extension graft is slightly over-sized such that it optimally engages with the self-expanding downstream contralateral leg. The balloon is then deflated and the second catheter assembly is removed in the manner previously described hereinabove with respect to the main catheter.
The directional catheter is also removed such that a second catheter assembly, on which is packaged a tubular graft extension, and which may be identical to the second catheter assembly, can be introduced over the primary guidewire and through the first introducer sheath assembly. This third catheter assembly is advanced until the distal end of the extension graft is at the bifurcation point of the aortic graft. In like manner to that previously described hereinabove, a third graft extension positioned on the third catheter assembly is deployed such that its upstream end is in contact with the ipsilateral leg of the aortic graft, and its downstream end is in contact with the right iliac artery. Also in like manner to that described hereinabove, the balloon on third catheter assembly is inflated to expand the balloon expandable extension graft in the ipsilateral side. In one embodiment of the present invention, the extension graft is slightly over-sized such that it optimally engages with the self-expanding downstream ipsilateral leg. In like manner to that previously described above, the balloon is deflated, extended proximally and then the third catheter assembly is withdrawn.
In an alternate embodiment both the ipsilateral and contralateral balloon catheters could be positioned simultaneously and inflated sequentially. While maintaining the position of the third catheter balloon the second catheter balloon is deflated and stretched and the second catheter is removed. The third catheter balloon is subsequently deflated, stretched, and removed.
The second sheath assembly and the stiff guidewires are withdrawn and the contralateral incision or puncture is sutured. An angiographic examination may take place to determine if the grafts are correctly placed and functioning. The first introducer sheath assembly is withdrawn and the right femoral incision is sutured. The result is a functioning trouser graft bridging an aneurysm.